Nightly flake: grpc generics compilation failure

https://fusion2.corp.google.com/invocations/264d140a-c367-473f-a5ec-225c9a4976bc/targets/cloud-devrel%2Fclient-libraries%2Fjava%2Fgoogle-cloud-java%2Fnightly%2Fgraalvm-sub-jobs%2Fnative-a%2Fgraalvm-native-5/log

```
07:17:01:908 [INFO] --- compiler:3.13.0:compile (default-compile) @ grpc-google-cloud-aiplatform-v1beta1 ---
07:17:01:911 [INFO] Recompiling the module because of changed dependency.
07:17:01:911 [INFO] Compiling 35 source files with javac [debug deprecation release 8] to target/classes
07:17:03:418 [INFO] -------------------------------------------------------------
07:17:03:418 [ERROR] COMPILATION ERROR :
07:17:03:418 [INFO] -------------------------------------------------------------
07:17:03:418 [ERROR] /tmpfs/src/github/google-cloud-java/java-aiplatform/grpc-google-cloud-aiplatform-v1beta1/src/main/java/com/google/cloud/aiplatform/v1beta1/PredictionServiceGrpc.java:[1901,19] incompatible types: inference variable ReqT has incompatible equality constraints com.google.cloud.aiplatform.v1beta1.GenerateContentResponse,ReqT,com.google.cloud.aiplatform.v1beta1.GenerateContentRequest
07:17:03:418 [INFO] 1 error
```